Thermal cameras are used worldwide especially to monitor large and nocturnal vertebrate species in open areas. As drone technology becomes more common, and digital thermal cameras can be connected to the equipment, a new Era for biodiversity evaluation is emerging. The monitoring of arboreal species in tropical regions is a huge challenge and the use of drones with thermal cameras has proven to be an excellent tool to reduce operational costs in searching and counting efforts. Since 2017, we have been using an S900 drone from DJI, which features a GoPro Hero4 and FLIR Vue Pro 336 13mm camera to monitor areas of occurrence of the Northern muriqui (Brachyteles hypoxanthus). We have flown more than 100 hours in different areas where the species occurs and we were able to record muriquis on at least 5 different occasions. At Parque Estadual Serra do Brigadeiro, we counted at least 22 individuals in just 8 minutes of flight, or about 7% of the population estimated during more than 1,700 hours of fieldwork over a 2-year period. The cost-benefit ratio of thermal cameras in drones is surprisingly high and the chances of increasing the effectiveness of the encounter rate and a counting accuracy of individuals are enormous, benefiting the actions of surveying and monitoring species of Neotropical large-bodied primates.